1,709 research outputs found
Near-infrared spatially resolved spectroscopy of (136108) Haumea's multiple system
The transneptunian region of the solar system is populated by a wide variety
of icy bodies showing great diversity. The dwarf planet (136108) Haumea is
among the largest TNOs and displays a highly elongated shape and hosts two
moons, covered with crystalline water ice like Hamuea. Haumea is also the
largest member of the sole TNO family known to date. A catastrophic collision
is likely responsible for its unique characteristics. We report here on the
analysis of a new set of observations of Haumea obtained with SINFONI at the
ESO VLT. Combined with previous data, and using light-curve measurements in the
optical and far infrared, we carry out a rotationally resolved spectroscopic
study of the surface of Haumea. We describe the physical characteristics of the
crystalline water ice present on the surface of Haumea for both regions, in and
out of the Dark Red Spot (DRS), and analyze the differences obtained for each
individual spectrum. The presence of crystalline water ice is confirmed over
more than half of the surface of Haumea. Our measurements of the average
spectral slope confirm the redder characteristic of the spot region. Detailed
analysis of the crystalline water-ice absorption bands do not show significant
differences between the DRS and the remaining part of the surface. We also
present the results of applying Hapke modeling to our data set. The best
spectral fit is obtained with a mixture of crystalline water ice (grain sizes
smaller than 60 micron) with a few percent of amorphous carbon. Improvements to
the fit are obtained by adding ~10% of amorphous water ice. Additionally, we
used the IFU-reconstructed images to measure the relative astrometric position
of the largest satellite Hi`iaka and determine its orbital elements. An orbital
solution was computed with our genetic-based algorithm GENOID and our results
are in full agreement with recent results.Comment: Accepted for publication in A&
The formation of the solar system
The solar system started to form about 4.56 Gyr ago and despite the long
intervening time span, there still exist several clues about its formation. The
three major sources for this information are meteorites, the present solar
system structure and the planet-forming systems around young stars. In this
introduction we give an overview of the current understanding of the solar
system formation from all these different research fields. This includes the
question of the lifetime of the solar protoplanetary disc, the different stages
of planet formation, their duration, and their relative importance. We consider
whether meteorite evidence and observations of protoplanetary discs point in
the same direction. This will tell us whether our solar system had a typical
formation history or an exceptional one. There are also many indications that
the solar system formed as part of a star cluster. Here we examine the types of
cluster the Sun could have formed in, especially whether its stellar density
was at any stage high enough to influence the properties of today's solar
system. The likelihood of identifying siblings of the Sun is discussed.
Finally, the possible dynamical evolution of the solar system since its
formation and its future are considered.Comment: 36 pages, 7 figures, invited review in Physica Script
Bose-Einstein Condensation of S = 1 Ni spin degrees of freedom in NiCl2-4SC(NH2)2
It has recently been suggested that the organic compound
NiCl-4SC(NH) (DTN) exhibits Bose-Einstein Condensation (BEC) of the
Ni spin degrees of freedom for fields applied along the tetragonal c-axis. The
Ni spins exhibit 3D XY-type antiferromagnetic order above a field-induced
quantum critical point at T. The Ni spin fluid can be
characterized as a system of effective bosons with a hard-core repulsive
interaction in which the antiferromagnetic state corresponds to a Bose-Einstein
condensate (BEC) of the phase coherent Ni spin system. We have
investigated the the high-field phase diagram and the occurrence of BEC in DTN
by means of specific heat and magnetocaloric effect measurements to dilution
refrigerator temperatures. Our results indicate that a key prediction of BEC is
satisfied; the magnetic field-temperature quantum phase transition line
approaches a power-law at low temperatures,
with an exponent at the quantum critical point,
consistent with the BEC theory prediction of .Comment: 4 pages, 4 figure
Danos causados por percevejos da panícula em grãos de arroz no Estado do Tocantins.
O objetivo deste trabalho foi avaliar materiais (linhagens/cultivares) de arroz quanto à resistência ao ataque de percevejos do gênero Oebalus sugadores das espiguetas e efeitos da alimentação destes insetos sobre o rendimento e grãos inteiros
Desenvolvimento inicial de cajueiro anão precoce, clone CCP 265, sob irrigação com água salina.
Resposta do arroz de sequeiro à adubação nitrogenada e espaçamento.
O objetivo deste trabalho foi avaliar a interação entre diferentes doses de nitrogênio sobre a produtividade de arroz de sequeiro cultivado em diferentes espaçamentos
Efeito da calagem e da adubação com fósforo e potássio sobre a produção de matéria seca, nodulação e teores de proteína bruta, fósforo e cálcio de leguminosas tropicais.
Foram estudados, em casa de vegetação, em Teresina, PI, a produção de nódulos, o peso da parte aérea e da raiz e os teores de PB, P e Ca das leguminosas forrageiras arbóreas angico-de-bezerro (P. moniliformis Benth.) e caneleiro (C. macrophyllum Tul.). Utilizaram-se vasos com duas plantas, e os tratamentos: testemunha, K, P, P + K, Cal, Cal + k, Cal + P e Cal + P + K. O solo foi coletado sob a copa de árvores de cada espécie..
Resistência a inseticidas piretróides em populações de Sitophilus zeamais (Coleoptera: curculionidae) coletadas em unidades armazenadoras de arroz no Estado do Tocantins.
O Estado do Tocantins tem um grande potencial agrícola, com extensas áreas propícias à prática da agricultura e, vem se destacando no cenário nacional como grande produtor de grãos, principalmente arroz, segunda cultura em área plantada, encontrando-se já instalados grandes complexos de armazenagem e beneficiamento. Nas unidades armazenadoras tocantinenses o uso de inseticidas para o controle preventivo ou curativo de insetos-praga é uma prática comum, o que levanta a suspeita das populações já terem desenvolvido resistência aos inseticidas usados em seu controle. Nesse contexto, informações sobre resistência a inseticidas para esta espécie são necessárias e úteis para implementação de programas de manejo de resistência a inseticidas
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